Apparatus and method for uplink data report and control channel synchronization in wireless communication system

ABSTRACT

A pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system, such as long term evolution (LTE). A user equipment (UE) in a wireless communication system is provided. The UE includes a transceiver, and at least one processor coupled to the transceiver and configured to generate a lone truncated buffer status report (BSR) based on a number of padding bits, and transmit the long truncated BSR informing of data volume for at least one logical channel group among logical channel groups having data for transmission, wherein the data volume for the at least one logical channel group is reported following an order that is determined based on a highest priority logical channel in each of the at least one logical channel group.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. 119(a)of a Korean patent application number 10-2018-0093109, filed on Aug. 9,2018, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a wireless communication system. Moreparticularly, to an apparatus and a method for uplink data reporting andcontrol channel synchronization in a wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post long term evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

A 5G system can provide various services to a terminal. To this end, theterminal can receive and transmit data from/to a base station. In casethat the terminal transmits data, the terminal receives an uplink grantfrom the base station so that resources are allocated to the terminal.At this time, in order to allocate uplink resources to the terminal, thebase station can check a buffer status for uplink data of the terminal.In addition, in order for the terminal to perform communication with thebase station, synchronization of wireless signals may be required.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providean apparatus and a method for uplink data reporting and control channelsynchronization in a wireless communication system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an embodiment of the disclosure, an apparatus and a methodis provided for efficiently transmitting a report on uplink data in awireless communication system.

According to an embodiment of the disclosure, an apparatus and a methodis provided for efficiently synchronizing a control channel in awireless communication system.

In accordance with an embodiment of the disclosure, a user equipment(UE) in a wireless communication system is provided. The UE includes atransceiver, and at least one processor coupled to the transceiver andconfigured to generate a lone truncated buffer status report (BSR) basedon a number of padding bits, and transmit the long truncated BSRinforming of data volume for at least one logical channel group amonglogical channel groups having data for transmission, wherein the datavolume for the at least one logical channel group is reported followingan order that is determined based on a highest priority logical channelin each of the at least one logical channel group.

In accordance with another embodiment of the disclosure, a base stationin a wireless communication system is provided. The base stationincludes a transceiver, and at least one processor coupled to thetransceiver and configured to receive, from a UE, a long truncated BSRinforming of data volume for at least one logical channel group amonglogical channel groups having data for transmission, the logical channelgroups being established at the UE, wherein the data volume for the atleast one logical channel group is reported following an order that isdetermined based on a highest priority logical channel in each of the atleast one logical channel group.

In accordance with another embodiment of the disclosure, a UE in awireless communication system is provided. The UE includes atransceiver, and at least one processor coupled to the transceiver andconfigured to receive, from a base station, first system informationcomprising a time-alignment-timer-common value, transmit, to the basestation, a random access preamble in order to transmit one of a firstmessage for requesting to resume a radio resource control (RRC)connection and a second message for requesting second systeminformation, receive, form the base station, a random access responsecomprising a timing advanced (TA) command, after transmitting the randomaccess preamble, start a time alignment timer that has a lengthindicated by the time-alignment-timer-common value, and transmit one ofthe first message and the second message.

The apparatus and method according to an embodiment can efficientlyreport the status of uplink data and enable synchronization of a controlchannel.

Effects which can be acquired by the disclosure are not limited to theabove described effects, and other effects that have not been mentionedmay be clearly understood by those skilled in the art from the followingdescription.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates a wireless communication system according to anembodiment of the disclosure;

FIG. 2 illustrates a configuration of a base station in a wirelesscommunication system according to an embodiment of the disclosure;

FIG. 3 illustrates a configuration of a terminal in a wirelesscommunication system according to an embodiment of the disclosure;

FIG. 4 illustrates a procedure for transmitting a buffer status report(BSR) message in a wireless communication system according to anembodiment of the disclosure;

FIG. 5 illustrates a case in which a terminal transmits a long truncatedBSR in a wireless communication system according to an embodiment of thedisclosure;

FIG. 6 illustrates a type of a long truncated BSR in a wirelesscommunication system according to an embodiment of the disclosure;

FIG. 7 illustrates setting of a priority that represents a logicalchannel group in a wireless communication system according to anembodiment of the disclosure;

FIG. 8 is a flowchart for selecting a logical channel group to bereported to a long truncated BSR in a wireless communication systemaccording to an embodiment of the disclosure;

FIG. 9 illustrates setting of a priority that represents a logicalchannel group in a wireless communication system according to anembodiment of the disclosure;

FIG. 10 is a flowchart for selecting a logical channel group to bereported to a long truncated BSR in a wireless communication systemaccording to an embodiment of the disclosure;

FIG. 11 illustrates an embodiment of a type of a long truncated BSR in awireless communication system according to an embodiment of thedisclosure;

FIG. 12 is a flowchart for selecting a logical channel group to bereported to a long truncated BSR in a wireless communication systemaccording to an embodiment of the disclosure;

FIG. 13 illustrates a procedure for resuming a radio resource control(RRC) connection between a terminal and a base station in a wirelesscommunication system according to an embodiment of the disclosure;

FIG. 14 illustrates an operation of a time alignment timer(TimeAlignmentTime) according to random access in a wirelesscommunication system according to an embodiment of the disclosure;

FIG. 15 illustrates a procedure in which a terminal receives systeminformation from a base station in a wireless communication systemaccording to an embodiment of the disclosure;

FIG. 16 is a flowchart illustrating a case in which TimeAlignmentTimerexpires in a wireless communication system according to an embodiment ofthe disclosure;

FIG. 17 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure;

FIG. 18 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure;

FIG. 19 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure;

FIG. 20 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure;

FIG. 21 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in an RRC resumption requestprocess in a wireless communication system according to an embodiment ofthe disclosure; and

FIG. 22 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The terms used in the disclosure are only used to describe specificembodiments of the disclosure, and are not intended to limit thedisclosure. A singular expression may include a plural expression unlessthey are definitely different in a context. Unless defined otherwise,all terms used herein, including technical and scientific terms, havethe same meaning as those commonly understood by a person skilled in theart to which the disclosure pertains. Such terms as those defined in agenerally used dictionary may be interpreted to have the meanings equalto the contextual meanings in the relevant field of art, and are not tobe interpreted to have ideal or excessively formal meanings unlessclearly defined in the disclosure. In some cases, even the term definedin the disclosure should not be interpreted to exclude embodiments ofthe disclosure.

Hereinafter, an embodiment of the disclosure will be described based onan approach of hardware. However, an embodiment of the disclosureinclude a technology that uses both hardware and software and thus, theembodiment of the disclosure may not exclude the perspective ofsoftware.

The disclosure relates to an apparatus and a method for transmittinginformation on uplink data and maintaining synchronization with a basestation in a wireless communication system.

It should be noted that the terms used in the following description,such as terms referring to signals, terms referring to channels, termsreferring to control information, terms referring to control parameters,terms referring to network entities, terms referring to components ofthe apparatus, and the like are illustrated for convenience ofexplanation. Accordingly, the disclosure is not limited to terms to bedescribed below, and other terms having equivalent technical meaningscan be used.

In addition, the disclosure describes an embodiment using terms used insome communication standards (e.g., 3rd Generation Partnership Project(3GPP)), but this is merely illustrative. The embodiment can be easilymodified and applied in other communication systems as well.

FIG. 1 illustrates a wireless communication system according to anembodiment of the disclosure.

Referring to FIG. 1, a base station 110, a terminal 120, and a terminal130 are illustrated as some of nodes using a wireless channel in awireless communication system. Although FIG. 1 illustrates only one basestation, it may further include another base station which is the sameas or similar to the base station 110.

The base station 110 is a network infrastructure that provides wirelessaccess to the terminals 120 and 130. The base station 110 has a coveragedefined by a certain geographic area based on a distance at whichsignals can be transmitted. The base station 110 may be referred to asan “access point (AP)”, an “evolved Node B (eNodeB)”, a “5th generation(5G) node”, “5G node B (gNobeB, gNB)”, a “wireless point”, or a“transmission/reception point (TRP)”, or may be referred to as otherterms having equivalent technical meanings thereto.

Each of the terminal 120 and the terminal 130 is a device used by a userand communicates with the base station 110 via a wireless channel. Insome cases, at least one of the terminal 120 and the terminal 130 can beoperated without user involvement. For example, at least one of theterminal 120 and the terminal 130 is a device for performing machinetype communication (MTC), and may not be carried by a user. Each of theterminal 120 and the terminal 130 may be referred to as a “userequipment (UE)”, a “mobile station”, a “subscriber station”, a “remoteterminal”, a “wireless terminal”, or a “user device”, or may be referredto as other terms having equivalent technical meanings thereto.

The base station 110, the terminal 120, and the terminal 130 maytransmit and receive wireless signals in a millimeter wave (mmWave) band(e.g., 28 GHz, 30 GHz, 38 GHz, or 60 GHz). At this time, in order toimprove a channel gain, the base station 110, the terminal 120, and theterminal 130 may perform beamforming. Here, beamforming may includetransmission beamforming and reception beamforming. For example, thebase station 110, the terminal 120, and the terminal 130 may assigndirectivity to transmission signals or reception signals. To this end,the base station 110 and the terminals 120 and 130 may select servingbeams 112, 113, 121, and 131 through a beam search or beam managementprocedure. After the serving beams 112, 113, 121, and 131 are selected,communication may then be performed through resources that are in aquasi co-located (QCL) relationship with resources that have transmittedthe serving beams 112, 113, 121, and 131.

If large-scale characteristics of a channel that transmits a symbol on afirst antenna port can be inferred from a channel that transmits asymbol on a second antenna port, it can be evaluated that the firstantenna port and the second antenna port are in a QCL relationship. Forexample, the large-scale characteristics may include at least one ofdelay spread, Doppler spread, Doppler shift, average gain, averagedelay, and spatial receiver parameter.

FIG. 2 illustrates a configuration of a base station in a wirelesscommunication system according to an embodiment of the disclosure. Theconfiguration illustrated in FIG. 2 can be understood as a configurationof the base station 110. Terms such as “ . . . unit”, “ . . . -er(-or)”, and the like used herein denote a unit for processing at leastone function or operation, and may be implemented by hardware, software,or a combination of hardware and software.

Referring to FIG. 2, a base station includes a wireless communicationunit 210, a backhaul communication unit 220, a storage unit 230, and acontroller 240.

The wireless communication unit 210 performs functions for transmittingand receiving signals via a wireless channel. For example, the wirelesscommunication unit 210 performs conversion between a baseband signal anda bit string according to a physical layer standard of the system. Forexample, at the time of transmitting data, the wireless communicationunit 210 generates complex symbols by encoding and modulating atransmission bit string. In addition, at the time of receiving data, thewireless communication unit 210 demodulates and decodes the basebandsignal to recover a reception bit string.

In addition, the wireless communication unit 210 up-converts a basebandsignal into a radio frequency (RF) band signal, transmits the RF bandsignal through an antenna, and down-converts the RF band signal receivedthrough the antenna into a baseband signal. To this end, the wirelesscommunication unit 210 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a digital to analogconverter (DAC), and an analog to digital converter (ADC). In addition,the wireless communication unit 210 may include a plurality oftransmission/reception paths. Further, the wireless communication unit210 may include at least one antenna array composed of a plurality ofantenna elements.

In terms of hardware, the wireless communication unit 210 may becomposed of a digital unit and an analog unit. The analog unit mayinclude a plurality of sub-units according to operating power, anoperating frequency, and the like. The digital unit may be implementedwith at least one processor (e.g., a digital signal processor {DSP}).

The wireless communication unit 210 transmits and receives signals asdescribed above. Accordingly, all or a part of the wirelesscommunication unit 210 may be referred to as a “transmitter”, a“receiver”, or a “transceiver”. In the following description, thetransmission and reception performed through a wireless channel are usedto mean that the above-described processing is performed by the wirelesscommunication unit 210.

The backhaul communication unit 220 provides an interface for performingcommunication with other nodes in a network. For example, the backhaulcommunication unit 220 converts bit strings transmitted from the basestation to other nodes, for example, another access node, another basestation, an upper node, a core network, and the like, into physicalsignals, and converts the physical signal received from the other nodesinto bit strings.

The storage unit 230 stores data, such as a basic program, anapplication program, configuration information, and the like, foroperation of the base station. The storage unit 230 may be composed of avolatile memory, a nonvolatile memory, or a combination of the volatilememory and the nonvolatile memory. The storage unit 230 provides thestored data in response to a request of the controller 240.

The controller 240 controls the overall operations of the base station.For example, the controller 240 transmits and receives signals throughthe wireless communication unit 210 or the backhaul communication unit220. In addition, the controller 240 records data in the storage unit230 and reads the recorded data. The controller 240 may performfunctions of a protocol stack required by a communication standard.According to another embodiment of the disclosure, the protocol stackmay be included in the wireless communication unit 210. To this end, thecontroller 240 may include at least one processor. According to anembodiment of the disclosure, the controller 240 may control the basestation to perform operations according to an embodiment describedbelow.

FIG. 3 illustrates a configuration of a terminal in a wirelesscommunication system according to an embodiment of the disclosure. Theconfiguration illustrated in FIG. 3 can be understood as a configurationof the terminal 120. Terms such as “ . . . unit”, “ . . . -er (-or)”,and the like used herein denote a unit for processing at least onefunction or operation, and may be implemented by hardware, software, ora combination of hardware and software.

Referring to FIG. 3, the terminal includes a communication unit 310, astorage unit 320, and a controller 330.

The communication unit 310 performs functions for transmitting andreceiving signals through a wireless channel. For example, thecommunication unit 310 performs conversion between a baseband signal anda bit string according to a physical layer standard of the system. Forexample, at the time of transmitting data, the communication unit 310generates complex symbols by encoding and modulating a transmission bitstring. In addition, at the time of receiving data, the communicationunit 310 demodulates and decodes the baseband signal to recover areception bit string. In addition, the communication unit 310up-converts a baseband signal into an RF band signal, transmits the RFband signal through an antenna, and down-converts the RF band signalreceived through the antenna into a baseband signal. For example, thecommunication unit 310 may include a transmission filter, a receptionfilter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

In addition, the communication unit 310 may include a plurality oftransmission/reception paths. Further, the communication unit 310 mayinclude at least one antenna array composed of a plurality of antennaelements. In terms of hardware, the communication unit 310 may becomposed of a digital circuit and an analog circuit (e.g., radiofrequency integrated circuit {RFIC}). The digital circuit and the analogcircuit may be implemented in one package. In addition, thecommunication unit 310 may include a plurality of RF chains. Further,the communication unit 310 may perform beamforming.

The communication unit 310 transmits and receives signals as describedabove. Accordingly, all or a part of the communication unit 310 may bereferred to as a “transmitter”, a “receiver”, or a “transceiver”. In thefollowing description, the transmission and reception performed througha wireless channel are used to mean that the above-described processingis performed by the communication unit 310.

The storage unit 320 stores data, such as a basic program, anapplication program, configuration information, and the like, foroperation of the terminal. The storage unit 320 may be composed of avolatile memory, a nonvolatile memory, or a combination of the volatilememory and the nonvolatile memory. The storage unit 320 provides thestored data in response to a request of the controller 330.

The controller 330 controls the overall operations of the terminal. Forexample, the controller 330 transmits and receives signals through thecommunication unit 310. In addition, the controller 330 records data inthe storage unit 320 and reads the recorded data. The controller 330 mayperform functions of a protocol stack required by a communicationstandard. To this end, the controller 330 may include at least oneprocessor or microprocessor, or may be a part of the processor. Inaddition, a part of the communication unit 310 and the controller 330may be referred to as a communication processor (CP). According to anembodiment of the disclosure, the controller 330 may control theterminal to perform operations according to an embodiment describedbelow.

FIG. 4 illustrates a procedure for transmitting a buffer status report(BSR) message in a wireless communication system according to anembodiment of the disclosure.

Referring to FIG. 4, in operation 401 the terminal 120 reports a datavolume of uplink data stored in a buffer in order to transmit the uplinkdata to the base station 110, which is referred to as “buffer statusreporting”. At this time, the reported data volume may not be for eachof all logical channels configured in the terminal. If the terminalreports the data volume for each of the configured logical channels, thesize of the BSR message reported if a plurality of logical channels areconfigured may become too large. An increase in the size of the BSRmessage may lead to a decrease in coverage or a depletion of radioresources. Accordingly, the terminal may classify the configured logicalchannels into a plurality of logical channel groups (LCGs), and mayindicate a sum of the data volume for all logical channels belonging toeach LCG for each LCG using the BSR message.

In the following description, it is understood that a “logical channelhaving data” means a logical channel related to data buffered in theterminal. For example, if the buffered data is to be transmitted througha specific logical channel, the specific logical channel may be referredto as the “logical channel having data”. Similar expressions can also beused for logical channel group (LCGs).

The BSR message can be classified into a periodic BSR, a regular BSR,and a padding BSR depending on the time during which the message istransmitted and an amount of information.

The periodic BSR is used to report a data volume to the base station atregular intervals. According to wireless communication procedures of thebase station and the terminal and the operation of a data application,the data volume buffered in the terminal may be changed in real-time. Inorder for the base station to continuously update the changed datavolume, periodic transmission of the BSR may be required. Fortransmission of the periodic BSR, the base station may configure aperiodic BSR timer value to the terminal. If the timer expires, theterminal performs a procedure of transmitting the periodic BSR.

The periodic BSR is transmitted on an event basis. For example, if it isnecessary to report the data volume to the base station due togeneration of new data for a logical channel having a higher prioritythan a logical channel that previously had data, or if data related to aspecific LCG is no longer generated, the periodic BSR is transmitted.Based on the periodic BSR, the base station may use the BSR for uplinkscheduling.

The padding BSR refers to a BSR included in the remaining resources ifresidual resources remain after data and a media access control (MAC)control element (CE) are included in an MAC protocol data unit (PDU)allocated to the terminal. If the padding BSR is not transmitted, thecorresponding radio resource is used as a simple padding so that theradio resource may be wasted. Therefore, by allowing the BSR to beincluded in the remaining resources, the terminal may transmit aresource status of the terminal to the base station. The communicationsystem may force or recommend the transmission of the padding BSR.

FIG. 5 illustrates a case in which a terminal transmits a long truncatedBSR in a wireless communication system according to an embodiment of thedisclosure. FIG. 5 illustrates examples of the padding BSR.

Referring to FIG. 5, if resources are left even though both data of alogical channel and an MAC CE 512 are filled in an uplink MAC PDU 510allocated to the terminal, the terminal may transmit the BSR using theremaining resource 514. Here, the type of the BSR to be transmitteddepends on the size of the remaining resources. In other words, as thepadding BSR using padding, what type of BSR to be transmitted may dependon the number of padding bits.

For example, if the amount of the remaining resources 514 is equal tothe size of each of a short BSR and an MAC sub-header 522 of the shortBSR, the short BSR may be included. In addition, even if there is onlyone LCG in which the terminal stores data, the terminal may transmit theshort BSR.

As another example, if the number of LCGs having data is two or more andthe amount of the remaining resources 514 is equal to or greater thanthe size of each of a long BSR including buffer sizes of all LCGs havingdata and an MAC sub-header 524 of the long BSR, the terminal maytransmit the long BSR. If the amount of the remaining resources 514 issmaller than the size of each of the long BSR including buffer sizes ofall LCGs having data and the MAC sub-header 524 of the long BSR andgreater than the size of each of the short BSR and the MAC sub-header522 of the short BSR, the terminal may transmit a long truncated BSR.Here, “truncated” means that it does not include buffer size informationof all LCGs having data, but includes buffer size information for someof the LCGs. At this time, the LCG of which the buffer size informationis included in the long truncated BSR may be determined according to apriority of the LCGs or a priority of logical channels included in theLCGs.

FIG. 6 illustrates a type of a long truncated BSR in a wirelesscommunication system according to an embodiment of the disclosure.

Referring to FIG. 6, a long truncated BSR may include LCGi fields 610 to617 indicating whether each LCG has data and buffer size fields 620,630, and 640 each indicating the data volume stored by an actual LCG.Here, an index i of the LCGi field denotes a logical channel groupidentifier (LCG ID) of the LCG. For example, an LCG3 field indicateswhether an LCG 3 has stored data. For example, the LCGi field set to “0”means that the corresponding LCG has no data, and the LCGi field set to“1” means that the corresponding LCG has data.

The long truncated BSR may include buffer sizes for some of all LCGs inwhich the LCGi field is indicated by “1”. In other words, if the numberof the LCGi fields indicated by “1” is n, n−1 or less buffer size fieldsmay exist. Thus, if the long truncated BSR is used, only the buffersizes for some LCGs selected from the LCGs including the logical channelhaving data are reported. In the embodiment of FIG. 6, the buffer sizes620, 630, and 640 of three LCGs are reported. If the BSR of FIG. 6 is along truncated BSR, four or more LCGi fields may be set to “1”.

FIG. 7 illustrates setting of a priority that represents a logicalchannel group in a wireless communication system according to anembodiment of the disclosure.

Referring to FIG. 7, it is assumed that a total of four logical channelsincluding a logical channel 1 711, a logical channel 2 712, a logicalchannel 3 713, and a logical channel 4 714 are set. In FIG. 7, thelogical channel 1 711 is set to an LCG 0 720, the logical channel 2 712and the logical channel 3 713 are set to an LCG 1 721, and the logicalchannel 4 714 is set to an LCG 2 722. In addition, in FIG. 7, a priority1 is assigned to the logical channel 1 711, a priority 2 is assigned tothe logical channel 2 712, a priority 3 is assigned to the logicalchannel 3 713, and the priority 2 is assigned to the logical channel 4714. In FIG. 7, a priority having a small value can be interpreted as ahigh priority.

The priority that each logical channel has and the LCG to which eachlogical channel belongs can be known through a radio resource control(RRC) setting message of the base station. If a long truncated BSR istriggered so that the terminal has to generate the long truncated BSR,the terminal should select some logical channels among LCGs includinglogical channels having data, and should transmit information on thebuffer size using the long truncated BSR. At this time, the terminal maydetermine whether to report the buffer size information of the LCG basedon the priority of each logical channel.

As in the embodiment of FIG. 7, the disclosure proposes an embodiment inwhich, in determining the priority of the LCG including at least onelogical channel having data if a long truncated BSR is generated, thepriority of the logical channel having the highest priority regardlessof whether each logical channel has data is used as a representativepriority of the corresponding LCG. The LCG 1 721 of FIG. 7 includes thelogical channel 2 712 and the logical channel 3 713, and if the longtruncated BSR is generated, the priority 2 of the logical channel 2 712having a higher priority between the logical channel 2 712 and thelogical channel 3 713 may be used as the priority of the LCG 1 721. Atthis time, the presence or absence of data of the logical channel 2 712and the logical channel 3 713 does not affect the priority determinationof the LCG 1 721. Accordingly, if the long truncated BSR is generated,the terminal may select LCGs to be reported in descending order orascending order of the priority of the logical channel with the highestpriority in the corresponding LCG, and may then report the buffer size.If there are LCGs with the same priority, the LCGs are prioritizedaccording to additional criteria. For example, the smaller the LCG IDnumber, the higher priority can be assigned, or the larger the logicalchannel ID number, the higher priority can be assigned.

According to the embodiment of FIG. 7, the priority of the logicalchannel with the highest priority in the LCG is determined as thepriority of the LCG, and the priority of the LCG determined iftransmitting the long truncated BSR is used. However, according toanother embodiment of the disclosure, the priority of the logicalchannel with the lowest priority in the LCG can be used as the priorityof the LCG. According to another embodiment of the disclosure, anaverage or median value of the priorities of all logical channels set inthe LCG can be used as the priority of the corresponding LCG. Accordingto the embodiment of FIG. 7, there is no possibility that an LCG inwhich the buffer size is reported to the long truncated BSR is variabledepending on the presence and absence of data of the logical channel.This allows the base station to know relatively precisely the buffersize of the LCG that has been reported.

The embodiment of FIG. 7 is equally applicable to a short truncated BSR.The terminal may report a data volume for an LCG including the logicalchannel with the highest priority among the LCGs including the logicalchannels having data, using the BSR. If there are LCGs having the samepriority, the priority of the LCG may be determined according toadditional other criteria. For example, the smaller the LCG ID number,the higher priority can be assigned, or the larger the logical channelID number, the higher priority can be assigned.

FIG. 8 is a flowchart for selecting an LCG to be reported to a longtruncated BSR in a wireless communication system according to anembodiment of the disclosure. FIG. 8 illustrates an operation method ofthe terminal 120.

Referring to FIG. 8, in operation 801 if a long truncated BSR is to betransmitted according to the conditions shown in the embodiment of FIG.5, the terminal selects at least one LCG to be included in the longtruncated BSR in operation 803. In operation 805, the terminal selectsthe priority of the logical channel having the highest priority or thelowest priority among the logical channels of each LCG, and determinesthe selected priority as a representative value of the LCG.

Next, in operation 807, the terminal allows the buffer size of at leastone LCG to be included in a long truncated BSR in descending order fromthe highest priority representative value of the LCG selected inoperation 805 or in ascending order from the lowest priorityrepresentative value thereof among the LCGs having data. At this time,each of the LCGi fields illustrated in FIG. 6 may be set to “1” for anLCG having a logical channel having actual data.

FIG. 9 illustrates setting of a priority that represents an LCG in awireless communication system according to an embodiment of thedisclosure.

Referring to FIG. 9, it is assumed that a total of four logical channelsincluding a logical channel 1 911, a logical channel 2 912, a logicalchannel 3 913, and a logical channel 4 914 are set. In FIG. 9, thelogical channel 1 911 is set to an LCG 0 920, the logical channel 2 912and the logical channel 3 913 are set to an LCG 1 921, and the logicalchannel 4 914 is set to an LCG 2 922. In addition, in FIG. 9, a priority1 is assigned to the logical channel 1 911, a priority 2 is assigned tothe logical channel 2 912, a priority 3 is assigned to the logicalchannel 3 913, and the priority 2 is assigned to the logical channel 4914. In FIG. 9, each LCG has a separate priority, the LCG 0 920 has thepriority 1, the LCG 1 921 has the priority 2, and the LCG 2 922 has thepriority 3. Here, a priority having a small value can be interpreted asa high priority. The priority that each logical channel has and the LCGto which each logical channel belongs can be known through an RRCsetting message of the base station. If a long truncated BSR istriggered so that the long truncated BSR has to be generated, theterminal has to select some logical channels among LCGs includinglogical channels having data and transmit buffer size information usingthe long truncated BSR. At this time, the terminal may determine whetherto report the buffer size information of the LCG based on the priorityof each logical channel. According to another embodiment of thedisclosure, the priority of the LCG may be determined based on thepriority of the logical channel, a logical channel ID, an LCG ID, andthe like.

As in the embodiment of FIG. 9, the disclosure proposes an embodiment inwhich, if a long truncated BSR is generated, the priority of the LCGwith the highest priority regardless of whether each logical channel hasdata is used in the LCG including logical channels having data. In otherwords, if the long truncated BSR is generated, the terminal may selectLCGs to be reported in descending order or ascending order of thepriority of the LCG with the highest priority in the corresponding LCG,and may then report the buffer size. If there are LCGs with the samepriority, the LCG of which the LCG ID number is small or large among theLCGs with the same priority may have a high priority.

According to the embodiment of FIG. 9, there is no possibility that anLCG in which the buffer size is reported to the long truncated BSR isvariable depending on the presence and absence of the stored data of thelogical channel. This allows the base station to know precisely thebuffer size of the LCG that has been reported. The embodiment of FIG. 9is equally applicable to a short truncated BSR. At this time, theterminal may report a data volume for an LCG with the highest priorityamong the LCGs including the logical channels having data at the time ofBSR. If there are LCGs having the same priority, the LCG of which theLCG ID number is small or large among the LCGs with the same prioritymay have a high priority.

FIG. 10 is a flowchart for selecting a logical channel group to bereported to a long truncated BSR in a wireless communication systemaccording to an embodiment of the disclosure. FIG. 10 illustrates anoperation method of the terminal 120.

Referring to FIG. 10, in operation 1001 if a long truncated BSR is to betransmitted according to the conditions shown in the embodiment of FIG.5, the terminal selects at least one LCG to be included in the longtruncated BSR in operation 1003. At this time, in operation 1005, theterminal may determine a preset priority of the LCG for each LCG as thepriority of the actual LCG. Next, in operation 1007, the terminalselects the LCGs in descending order from the highest priorityrepresentative value of the LCG selected in operation 1005 or inascending order from the lowest priority representative value thereofamong the LCGs having the stored data, and allows the buffer size of thecorresponding LCG to be included in the long truncated BSR. At thistime, each of the LCGi fields illustrated in FIG. 6 may be set to “1”for an LCG having a logical channel having actually stored data.

FIG. 11 illustrates an embodiment of a type of a long truncated BSR in awireless communication system according to an embodiment of thedisclosure.

Referring to FIG. 11, a long truncated BSR may include LCGi fields 1110to 1117 each indicating whether each LCG stores data, buffer size fields1120, 1130, and 1140 each indicting a data volume stored by an actualLCG, LCG ID fields 1125, 1135, and 1145 each indicating the LCGrepresented by the buffer size field. Here, an index i of the LCGi fielddenotes an LCG ID of the LCG. For example, an LCG3 field indicateswhether an LCG 3 has stored data. For example, the LCGi field set to “0”means that the corresponding LCG does not have the stored data, and theLCGi field set to “1” means that the corresponding LCG has the storeddata. In the case of a long truncated BSR, the buffer size for all LCGswhose LCGi field is represented by “1” cannot be included in the BSR. Inthis case, only the buffer size for the selected LCG among the LCGsincluding the logical channel having the stored data is reported.

The embodiment of FIG. 11 illustrates that buffer sizes 1120, 1130, and1140 of three LCGs are reported. If the BSR of FIG. 11 is a longtruncated BSR, four or more LCGi(s) may be represented by “1”. At thistime, the base station may not know exactly the buffer size of the LCGthat has been reported. To address this issue, the LCG ID fields 1125,1135, and 1145 can be used to indicate the LCG ID corresponding to thefollowing buffer size fields 1120, 1130, 1140. Thus, in the embodimentof FIG. 11, the buffer size field is reduced to 5 bits, and a buffersize index corresponding to a 5-bit buffer size table used in the shortBSR can be used. However, according to an embodiment of the disclosure,an existing 8-bit buffer size table may be used and the actual buffersize field may also be 8 bits. In this case, the LCG ID and the buffersize cannot be expressed in one byte.

FIG. 12 is a flowchart for selecting an LCG to be reported to a longtruncated BSR in a wireless communication system according to anembodiment of the disclosure. FIG. 12 illustrates an operation method ofthe terminal 120.

Referring to FIG. 12, in operation 1201 if a long truncated BSR is to betransmitted according to the conditions shown in the embodiment of FIG.5, the terminal selects an LCG to be included in the long truncated BSRin operation 1203. In operation 1205, the terminal determines a priorityof a logical channel having the highest priority among LCGs having datafor each LCG as the priority of the corresponding LCG. Next, inoperation 1207, the terminal selects the LCGs in descending order fromthe highest priority representative value of the LCG selected inoperation 1205 or in ascending order from the lowest priorityrepresentative value thereof among the LCGs having stored data, andallows the buffer size of the corresponding LCG to be included in thelong truncated BSR. At this time, in order to determine that the buffersize of the LCG that has been reported, the terminal may include LCG IDs(e.g., LCG IDs 1125, 1135, and 1145 of FIG. 11). At this time, the LCGifield of FIG. 11 may be set to “1” for the LCG having a logical channelhaving actually stored data.

According to the embodiment described above, the terminal may transmit areport for uplink data, that is, a BSR to the base station. In addition,the disclosure further describes an embodiment for a common controlchannel (CCCH).

Resumption of an RRC connection refers to a procedure in which an RRCconnection state between a terminal and a base station is switched froman RRC inactive mode to an RRC connected mode. In the case of anexisting 4th generation (4G) mobile communication system (e.g., a longterm evolution (LTE) system), the RRC connection state is classifiedinto an idle mode and a connected mode. However, at the time ofswitching from the RRC idle mode to the connected mode, it is timeconsuming and the procedure in the network is complicated, so that theswitching from the idle mode to the connected mode can be a burden onthe system. Specifically, in order for the terminal in the idle mode toswitch to the connected mode, after an RRC connection reestablishmentrequest, the base station must retrieve the context of the terminal froma network device, such as a mobility management entity (MME), and aprocedure for security is required. In addition, since an S1 interfacebetween the base station and a serving gateway (S-GW) needs to bereestablished, the burden on the system may increase if the idle modeand the connected mode are frequently switched. Accordingly, in the caseof the 5G mobile communication (e.g., NR), the inactive mode is defined.In the inactive mode, the terminal and the base station store thecontext of the terminal and can maintain an S1 bearer if necessary.Therefore, if the terminal in the inactive mode attempts to reconnect tothe network, the terminal may connect to the network faster with fewersignaling procedures through an RRC resumption procedure and maytransmit data.

FIG. 13 illustrates a procedure for resuming an RRC connection between aterminal and a base station in a wireless communication system accordingto an embodiment of the disclosure.

Referring to FIG. 13, in operation 1301 the terminal 120 operates in anRRC inactive mode. If the terminal 120 in the inactive mode desires toswitch to the connected mode, the terminal 120 performs camping on acell, and then transmits an RRC resumption request message to the basestation in operation 1303. Since the RRC resumption request message is amessage transmitted before the RRC connection is established, the RRCresumption request message is transmitted through a CCCH, and istransmitted using only the settings necessary for message transmission.In this case, in order to receive allocation of uplink resources fortransmitting the RRC resumption request message, the terminal 120performs a random access procedure prior to operation 1303. The randomaccess procedure may include operations in which the terminal 120transmits a random access preamble to the base station 110 and the basestation 110 transmits a random access response message to the terminal120. The details of the random access will be described with referenceto FIG. 14.

After receiving the RRC resumption request message of the terminal 120,in operation 1305, the base station 110 transmits an RRC resumptionmessage to the terminal 120 to instruct the terminal 120 to switch tothe RRC connected mode. The RRC resumption message may includeconfiguration information to be used by the terminal 120 in a connectedstate, and the terminal 120 may apply the corresponding configurationinformation. Next, in operation 1307, the terminal 120 operates in theRRC connected mode.

The terminal may switch from the inactive mode or the idle mode to theconnected mode, or perform a random access operation for anotherpurpose. The random access is divided into contention-based randomaccess and contention-free random access. FIG. 14 illustratescompetition-based random access.

FIG. 14 illustrates an operation of a time alignment timerTimeAlignmentTime according to random access in a wireless communicationsystem according to an embodiment of the disclosure.

Referring to FIG. 14, in the inactive mode or the idle mode, theterminal 120 cannot receive allocation of resources for transmitting amessage 3 to the base station 110. Thus, in operation 1401, the terminal120 receives allocation of radio resources to transmit the message 3 tothe base station 110. In operation 1401, for uplink synchronization, theterminal 120 transmits a random access preamble to the base station 110.Resources for transmitting the random access preamble may be resourceswhich are set by the base station 110 in advance using systeminformation. However, since the resources for transmitting the randomaccess preamble are not resources monopolized by a specific terminal, acollision may occur due to a plurality of terminals transmitting therandom access preamble at the same time.

After receiving the random access preamble, in operation 1403, the basestation 110 transmits a random access response (RAR) message to informthe terminal 120 of the reception of the random access preamble. The RARmessage may include a timing advance command, an uplink grant, atemporary cell-radio network temporary identifier (C-RNTI), and thelike. Among these, the timing advance command includes information forthe terminal 120 to adjust transmission timing for uplinksynchronization. The terminal 120 performs uplink synchronization withthe base station 110 by advancing or lagging the transmission timing tothe base station 110 according to a value indicated by a timing advancecommand field. The terminal 120 having received the timing advancecommand starts a TimeAlignmentTimer. While the TimeAlignmentTimer isoperating, the value indicated by the timing advance command field isvalid. In other words, while the TimeAlignmentTimer is operating, theterminal 120 can know that uplink synchronization with the base station110 has been performed.

An uplink grant field indicates uplink resources to which the terminal120 transmits the message 3 to the base station. The message 3 may beone of an RRC connection setup request message, an RRC connectionreestablishment request message, an RRC resumption request message, anda system information request message according to the situation of theterminal 120. In operation 1405, the base station 110 receives themessage 3. Next, in operation 1407, the base station 110 transmits amessage 4. The message 4 may include one of an RRC connection setupmessage, an RRC connection reestablishment message, an RRC resumptionmessage, and a system information message according to the content ofthe message 3. Next, in operation 1409, the terminal 120 transmits amessage 5 to the base station 110 to notify that the configuration up tothe message 4 is completed.

The system information refers to information indicating a commonconfiguration of the base station or a wireless network, and theterminal must acquire the content of the system information beforeestablishing an RRC connection. The system information may be classifiedinto essential system information that the terminal must know beforetransmitting a radio signal to the base station, and optional systeminformation that the terminal can request and receive from the basestation. The essential system information may be broadcasted from thebase station at regular intervals. For example, resources fortransmitting a random access preamble or information that must beperformed at the time of receiving the random access response messagemay be included in the essential system information.

FIG. 15 illustrates a procedure in which a terminal receives systeminformation from a base station in a wireless communication systemaccording to an embodiment of the disclosure. In FIG. 15, the essentialsystem information is referred to as “system information block 1(SIB1)”.

Referring to FIG. 15, in operation 1501 the terminal 120 may receive theSIB1 from the base station 110 through periodic monitoring. The SIB1 mayinclude a time value (e.g., TimeAlignmentTimerCommon value) that can beused as the time of the TimeAlignmentTimer that starts after receivingthe timing advance command included in the random access responsemessage.

Next, if there is necessary system information even though it is notincluded in the SIB1, the terminal 120 transmits a system informationrequest message to the base station 110 in operation 1503. The systeminformation request message is an example of the message 3 in FIG. 14,and can be transmitted via a CCCH. Accordingly, in operation 1505, thebase station 110 transmits the system information message, and theterminal 120 applies the received system information.

FIG. 16 is a flowchart illustrating a case in which TimeAlignmentTimerexpires in a wireless communication system according to an embodiment ofthe disclosure. FIG. 16 illustrates an operation method of the terminal120.

Referring to FIG. 16, the TimeAlignmentTimer of the terminal is startedor restarted if receiving the timing advance command message from thebase station. While the TimeAlignmentTimer is operating, uplinksynchronization between the terminal and the base station can beregarded as being performed. If the TimeAlignmentTimer expires inoperation 1601, the terminal determines whether the expiredTimingAlignmentTimer is a timer for a primary timing advance group(PTAG) in operation 1603. If the expired TimingAlignmentTimer is thetimer for PTAG, in operation 1605, the terminal empties a hybridautomatic repeat request (HARQ) buffer for all serving cells, releases aphysical uplink control channel (PUCCH) for all serving cells, andreleases a sounding reference signal (SRS) of all serving cells. Inaddition, the terminal may release all configured grants set in thedownlink and the uplink and may process all other TimeAlignmentTimers asexpired. If the expired TimingAlignmentTimer is not the timer for PTAG,the expired timer is a timer for a secondary timing advance group(STAG). In this case, in operation 1607, the terminal performs anasynchronous operation for the corresponding timing advance group (TAG).Specifically, the terminal can empty all HARQ buffers, release thePUCCH, release the SRS, and release the downlink and uplink configuredgrants.

FIG. 17 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure. FIG. 17 illustratesan operation method of the terminal 120.

Referring to FIG. 17, in operation 1701 the terminal performs camping onan NR cell. For example, in order to switch from the idle mode or theinactive mode to the connected mode, the terminal first performs campingon the cell. The embodiment of FIG. 17 illustrates that camping on a(3GPP NR) cell is performed. After performing camping on the cell, inoperation 1703, the terminal receives the SIB1 from the base station ofthe corresponding cell. The SIB1 is the essential system informationdescribed in FIG. 15, and includes configuration information necessaryfor the terminal to transmit a radio signal, such as a random accesspreamble to the base station. In operation 1705, the terminal receives atimeAlignmentTimerCommon value and a random access channel (RACH)-confignecessary for random access from the SIB 1. By configuring theRACH-config, the terminal can know the location of the radio resourcefor performing random access on the corresponding base station and theusable random access preamble. Next, in operation 1707, the terminalperforms a random access operation and prepares to transmit a messagecorresponding to the CCCH, that is, a service data unit (SDU).

However, if receiving the random access response message, the terminalmust start the TimeAlignmentTimer. At this time, it is necessary toconfigure a timer value to be used, and the timer value to be used maybe classified depending on the type of the message (e.g., SDU)transmitted to the CCCH. The embodiment of FIG. 17 illustrates that theused timer value varies depending on whether the message transmitted bythe terminal through the CCCH is an RRC resumption request message.

In operation 1709, the terminal determines whether the CCCH SDU is theRRC resumption request message. If the transmitted message is the RRCresumption request message, the terminal uses the TimeAlignmentTimervalue of access stratum (AS) context stored in the terminal as a valueof the corresponding timer in operation 1711. On the other hand, if thetransmitted message is not the RRC resumption request message, that is,if a CCCH message is the RRC connection setup request message, the RRCconnection reestablishment request message, or the system informationrequest message, the terminal uses the timeAlignmentTimerCommon valueincluded in the SIB1 as the value of the TimeAlignmentTimer in operation1713. As another example, the terminal may start the TimeAlignmentTimerusing a timer value configured in advance as a default value instead ofthe TimeAlignmentTimerCommon value. The default value may be set by thebase station to which the terminal has previously connected, or may be avalue set in the terminal during the process in which the terminal ismanufactured.

Next, in operation 1715, the terminal actually transmits the randomaccess preamble and receives the random access response message. Ifreceiving the timing advance command in the random access responsemessage, in operation 1717, the terminal applies the correspondingtiming advance command and starts the TimeAlignmentTimer using the valueof the previously determined TimeAlignmentTimer. Next, the terminal maytransmit the CCCH message using the radio resource indicated by anuplink (UL) grant field in the random access response message. Next, inoperation 1719, the terminal receives a response message to the CCCHmessage transmitted from the base station. For example, if the CCCHmessage transmitted by the terminal is the RRC resumption requestmessage, the terminal receives the RRC resumption message from the basestation. If the TimeAlignmentTimer value to be used by the terminal isconfigured in the CCCH message received from the base station inoperation 1721, the terminal uses the configured value and deletes thevalue applied to the TimeAlignmentTimer.

FIG. 18 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure. FIG. 18 illustratesan operation method of the terminal 120.

Referring to FIG. 18, in operation 1801 the terminal performs camping onan NR cell. For example, in order for the terminal to switch from theidle mode or the inactive mode to the connected mode, the terminal firstperforms camping on the cell. The embodiment of FIG. 18 illustrates thatcamping on a 3GPP NR cell is performed. After performing camping on thecell, in operation 1803, the terminal receives the SIB1 from the basestation of the corresponding cell. The SIB1 is the essential systeminformation described in FIG. 15, and includes configuration informationnecessary for the terminal to transmit a radio signal, such as a randomaccess preamble to the base station. In operation 1805, the terminalreceives a timeAlignmentTimerCommon value and an RACH-config necessaryfor random access from the SIB1. By configuring the RACH-config, theterminal can know the location of the radio resource for performingrandom access on the corresponding base station and the usable randomaccess preamble. Next, in operation 1807, the terminal performs a randomaccess operation and prepares to transmit a message corresponding to theCCCH, that is, a SDU.

If receiving the random access response message, the terminal must startthe TimeAlignmentTimer. At this time, it is necessary to configure atimer value to be used, and the timer value to be used may be classifieddepending on the type of the message (e.g., SDU) transmitted through theCCCH. The embodiment of FIG. 18 illustrates that the used timer valuevaries depending on a group of the message transmitted by the terminalthrough the CCCH. According to an embodiment of the disclosure, messagestransmitted through the CCCH can be classified into a first messagegroup and a second message group as shown in Table 1 below.

TABLE 1 First message group Second message group First RRC resumptionrequest Other CCCH message embodiment Second RRC resumption request,Other CCCH message embodiment system information request Third Systeminformation request Other CCCH message embodiment

In addition, the classification between the first message group and thesecond message group can be variously defined.

In operation 1809, the terminal determines whether a CCCH SDU belongs tothe first message group. If the transmitted message is the messagebelonging to the first message group, in operation 1811, the terminaluses the TimeAlignmentTimer value of the AS context used in the previousconnected mode and stored in the terminal as the value of thecorresponding timer. If the transmitted message is not the messagebelonging to the first message group, that is, if the corresponding CCCHmessage is the RRC connection setup request message, the RRC connectionreestablishment request message, or the system information requestmessage, in operation 1813, the terminal uses thetimeAlignmentTimerCommon value included in the SIB1 as the value of theTimeAlignmentTimer. As another example, the terminal may start theTimeAlignmentTimer using a timer value configured in advance as adefault value instead of the TimeAlignmentTimerCommon value. The defaultvalue may be set by the base station to which the terminal haspreviously connected, or may be a value set in the terminal during theprocess in which the terminal is manufactured.

Next, in operation 1815, the terminal transmits the random accesspreamble and receives the random access response message. If receivingthe timing advance command in the random access response message, inoperation 1817, the terminal applies the corresponding timing advancecommand and starts the TimeAlignmentTimer using the value of thepreviously determined TimeAlignmentTimer. Next, in operation 1819, theterminal transmits the CCCH message using radio resources indicated bythe uplink grant field in the random access response message. Next, inoperation 1819, the terminal receives a response message to the CCCHmessage transmitted by the base station. For example, if the CCCHmessage transmitted by the terminal is the RRC resumption requestmessage, the terminal receives the RRC resumption message from the basestation. If the TimeAlignmentTimer value to be used by the terminal isconfigured in the CCCH message received from the base station, inoperation 1821, the terminal uses the configured value and deletes thevalue applied to the TimeAlignmentTimer that is previously used.

FIG. 19 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure. FIG. 19 illustratesan operation method of the terminal 120.

Referring to FIG. 19, in operation 1901 the terminal performs camping onan NR cell. For example, in order for the terminal to switch from theidle mode or the inactive mode to the connected mode, the terminal firstperforms camping on the cell. The embodiment of FIG. 19 illustrates thatcamping on a 3GPP NR cell is performed. After performing camping on thecell, in operation 1903, the terminal receives the SIB1 from the basestation of the corresponding cell. The SIB1 is the essential systeminformation described in FIG. 15, and includes configuration informationnecessary for the terminal to transmit a radio signal, such as a randomaccess preamble to the base station. In operation 1905, the terminalreceives a timeAlignmentTimerCommon value and an RACH-config necessaryfor random access from the SIB1. By configuring the RACH-config, theterminal can know the location of the radio resource for performingrandom access on the corresponding base station and the usable randomaccess preamble. Next, in operation 1907, the terminal performs a randomaccess operation and prepares to transmit a message corresponding to theCCCH, that is, a SDU.

If receiving the random access response message, the terminal must theTimeAlignmentTimer. At this time, it is necessary to configure a timervalue to be used, and the timer value to be used may be classifieddepending on the type of the message (e.g., SDU) transmitted through theCCCH. The embodiment of FIG. 19 illustrates that the used timer valuevaries depending on whether the message transmitted through the CCCH isthe RRC resumption request message.

In operation 1909, the terminal determines whether a CCCH SDU is the RRCresumption request message. If the transmitted message is the RRCresumption request message, in operation 1911, the terminal determinesthe timeAlignmentTimerCommon value included in the SIB1 as theTimeAlignmentTimer value of the PTAG, and uses the TimeAlignmentTimervalue of the stored AS context as the TimeAlignmentTimer value of theSTAG. If the transmitted message is not the RRC resumption requestmessage, that is, if the corresponding CCCH message is the RRCconnection setup request message, the RRC connection reestablishmentrequest message, or the system information request message, in operation1913, the terminal uses the timeAlignmentTimerCommon value included inthe SIB1 as the TimeAlignmentTimer value. As another example, theterminal may start the TimeAlignmentTimer using a timer value configuredin advance as a default value instead of the TimeAlignmentTimerCommonvalue. The default value may be set by the base station to which theterminal has previously connected, or may be a value set in the terminalduring the process in which the terminal is manufactured.

Next, in operation 1915, the terminal transmits the random accesspreamble and receives the random access response message. If receivingthe timing advance command in the random access response message, inoperation 1917, the terminal applies the corresponding timing advancecommand and starts the TimeAlignmentTimer using the value of thepreviously determined TimeAlignmentTimer. Next, the terminal maytransmit the CCCH message using the radio resource indicated by anuplink grant field in the random access response message. Next, inoperation 1919, the terminal receives a response message to the CCCHmessage transmitted from the base station. For example, if the CCCHmessage transmitted by the terminal is the RRC resumption requestmessage, the terminal receives the RRC resumption message from the basestation. If the TimeAlignmentTimer value to be used by the terminal isconfigured in the CCCH message received from the base station, inoperation 1921, the terminal uses the configured value and deletes thevalue applied to the TimeAlignmentTimer.

FIG. 20 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure. FIG. 20 illustratesan operation method of the terminal 120.

Referring to FIG. 20, in operation 2001 the terminal performs camping onan NR cell. For example, in order for the terminal to switch from theidle mode or the inactive mode to the connected mode, the terminal firstperforms camping on the cell. The embodiment of FIG. 20 illustrates thatcamping on a 3GPP NR cell is performed. After performing camping on thecell, in operation 2003, the terminal receives the SIB1 from the basestation of the corresponding cell. The SIB1 is the essential systeminformation described in FIG. 15, and includes configuration informationnecessary for the terminal to transmit a radio signal, such as a randomaccess preamble to the base station. In operation 2005, the terminalreceives a timeAlignmentTimerCommon value and an RACH-config necessaryfor random access from the SIB1. By configuring the RACH-config, theterminal can know the location of the radio resource for performingrandom access on the corresponding base station and the usable randomaccess preamble. Next, in operation 2007, the terminal performs a randomaccess operation and prepares to transmit a message corresponding to theCCCH, that is, a SDU.

If receiving the random access response message, the terminal must startthe TimeAlignmentTimer. At this time, it is necessary to configure atimer value to be used, and the timer value to be used may be classifieddepending on the type of the message (e.g., SDU) transmitted through theCCCH. The embodiment of FIG. 20 illustrates that the used timer valuevaries depending on a group of the message transmitted by the terminalthrough the CCCH. According to embodiments of the disclosure, messagestransmitted through the CCCH can be classified into a first messagegroup and a second message group as shown in Table 2 below.

TABLE 2 First message group Second message group First RRC resumptionrequest Other CCCH message embodiment Second RRC resumption request,Other CCCH message embodiment system information request Third Systeminformation request Other CCCH message embodiment

In addition, the classification between the first message group and thesecond message group can be variously defined.

In operation 2009, the terminal determines whether a CCCH SDU belongs tothe first message group. If the transmitted message is the messagebelonging to the first message group, in operation 2011, the terminaldetermines the timeAlignmentTimerCommon value included in the SIB1 asthe TimeAlignmentTimer value of the PTAG, and uses theTimeAlignmentTimer value of the stored AS context as theTimeAlignmentTimer value of the STAG. If the transmitted message is notthe message belonging to the first message group, that is, if thecorresponding CCCH message is the RRC connection setup request message,the RRC connection reestablishment request message, or the systeminformation request message, in operation 2013, the terminal uses thetimeAlignmentTimerCommon value included in the SIB1 as the value of theTimeAlignmentTimer. As another example, the terminal may start theTimeAlignmentTimer using a timer value configured in advance as adefault value instead of the TimeAlignmentTimerCommon value. The defaultvalue may be set by the base station to which the terminal haspreviously connected, or may be a value set in the terminal during theprocess in which the terminal is manufactured.

Next, in operation 2015, the terminal transmits the random accesspreamble and receives the random access response message. If receivingthe timing advance command in the random access response message, inoperation 2017, the terminal applies the corresponding timing advancecommand and starts the TimeAlignmentTimer using the value of thepreviously determined TimeAlignmentTimer. Next, in operation 2019, theterminal transmits the CCCH message using radio resources indicated bythe uplink grant field in the random access response message. Next, inoperation 2019, the terminal receives a response message to the CCCHmessage transmitted by the base station. For example, if the CCCHmessage transmitted by the terminal is the RRC resumption requestmessage, the terminal receives the RRC resumption message from the basestation. If the TimeAlignmentTimer value to be used by the terminal isconfigured in the CCCH message received from the base station, inoperation 2021, the terminal uses the configured value and deletes thevalue applied to the TimeAlignmentTimer that is previously used.

FIG. 21 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in an RRC resumption requestprocess in a wireless communication system according to an embodiment ofthe disclosure. FIG. 21 illustrates an operation method of the terminal120. FIG. 21 illustrates that camping on a 3GPP NR cell is performed.

Referring to FIG. 21, in operation 2101 the terminal performs camping onan NR cell. For example, in order for the terminal to switch from theidle mode or the inactive mode to the connected mode, the terminal firstperforms camping on the cell. After performing camping on the cell, inoperation 2103, the terminal receives the SIB1 from the base station ofthe corresponding cell. The SIB1 is the essential system informationdescribed in FIG. 15, and includes configuration information necessaryfor the terminal to transmit a radio signal, such as a random accesspreamble to the base station. In operation 2105, the terminal receives atimeAlignmentTimerCommon value and an RACH-config necessary for randomaccess from the SIB 1. Based on the RACH-config, the terminal can knowthe location of the radio resource for performing random access on thecorresponding base station and the usable random access preamble. Next,in operation 2107, the terminal performs a random access operation andprepares to transmit an RRC resumption message corresponding to theCCCH.

Next, in operation 2111, the terminal transmits the random accesspreamble and receives the random access response message including thetiming advance command. If receiving the random access response message,the terminal starts the TimeAlignmentTimer. At this time, a timer valueto be used must be configured. In the case of the embodiment of FIG. 21,in operation 2109, the terminal determines the timer value based on thetimeAlignmentTimerCommon value included in the SIB1 and theTimeAlignmentTimer value. The timer value may be configured beforereceiving the random access response message or after receiving therandom access response message.

If receiving the timing advance command in the random access responsemessage, in operation 2113, the terminal applies the correspondingtiming advance command and starts the TimeAlignmentTimer using the valueof the TimeAlignmentTimer determined based on the SIB 1. Next, theterminal may transmit the RRC resumption request message through theCCCH using the radio resources indicated by the uplink grant field inthe random access response message.

Next, in operation 2115, the terminal receives the RRC resumptionmessage that is a response to the RRC resumption request messagetransmitted by the base station. If the TimeAlignmentTimer value to beused by the terminal is configured in the RRC resumption messagereceived from the base station, in operation 2117, the terminal uses theconfigured value and deletes the value applied to the TimeAlignmentTimerthat is previously used. As another example, the terminal may start theTimeAlignmentTimer using a timer value configured in advance as adefault value instead of the TimeAlignmentTimerCommon value. The defaultvalue may be set by the base station to which the terminal haspreviously connected, or may be a value set in the terminal during theprocess in which the terminal is manufactured.

As described with reference to FIGS. 17 to 21, if the terminal transmitsthe CCCH message, the TimeAlignmentTimer value configured by theterminal does not exist in the base station, so that the terminal mayuse the TimeAlignmentTimerCommon included in SIB1 or use the AS contextthat is previously used and stored. However, the TimeAlignmentCommonvalue may not be included in the SIB1, or the AS context stored by theterminal may not exist. In this case, it is difficult for the terminalto apply the TimeAlignmentTimer value. An operation if the configuredTimeAlignmentTimer value does not exist is shown in FIG. 22 below.

FIG. 22 is a flowchart illustrating a case in which a terminalconfigures a value of TimeAlignmentTimer in a wireless communicationsystem according to an embodiment of the disclosure. FIG. 22 illustratesan operation method of the terminal 120.

Referring to FIG. 22, in operation 2201 the terminal receives the timingadvance command. If the terminal receives the timing advance command ina random access response or in another method, the terminal maydetermine whether the TimeAlignmentTimer value configured in a currentcell or a current base station exists in operation 2203. If theconfigured TimeAlignmentTimer value does not exist, in operation 2205,the terminal may not start the TimeAlignmentTimer because there is notimer value to be applied. Alternatively, according to anotherembodiment of the disclosure, it is possible to start theTimeAlignmentTimer using the timer value configured as the default valuein advance. If the configured TimeAlignmentTimer value exists, inoperation 2207, the terminal may start the TimeAlignmentTimer using theconfigured value.

The embodiment described with reference to FIG. 22 can be applied onlyin a case of transmitting at least one message of the RRC resumptionrequest message, the system information request message, and the RRCsetup connection message. However, the disclosure is not limitedthereto.

Methods according to embodiments stated in claims and/or specificationsof the disclosure may be implemented in hardware, software, or acombination of hardware and software.

If the methods are implemented by software, a computer-readable storagemedium for storing one or more programs (software modules) may beprovided. The one or more programs stored in the computer-readablestorage medium may be configured for execution by one or more processorswithin the electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to an embodiment of the disclosure as defined by the appendedclaims and/or disclosed herein.

The programs (software modules or software) may be stored in nonvolatilememories including a random access memory and a flash memory, a readonly memory (ROM), an electrically erasable programmable read onlymemory (EEPROM), a magnetic disc storage device, a compact disc-ROM(CD-ROM), digital versatile discs (DVDs), or other type optical storagedevices, or a magnetic cassette. Alternatively, any combination of someor all of the may form a memory in which the program is stored. Further,a plurality of such memories may be included in the electronic device.

In addition, the programs may be stored in an attachable storage devicewhich is accessible through communication networks, such as theInternet, Intranet, local area network (LAN), wide area network (WAN),and storage area network (SAN), or a combination thereof. Such a storagedevice may access the electronic device via an external port. Further, aseparate storage device on the communication network may access aportable electronic device.

In the above-described detailed embodiments of the disclosure, acomponent included in the disclosure is expressed in the singular or theplural according to a presented detailed embodiment. However, thesingular form or plural form is selected for convenience of descriptionsuitable for the presented situation, and an embodiment of thedisclosure are not limited to a single element or multiple elementsthereof. Further, either multiple elements expressed in the descriptionmay be configured into a single element or a single element in thedescription may be configured into multiple elements.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver; and at least one processorcoupled to the transceiver and configured to: generate a lone truncatedbuffer status report (BSR) based on a number of padding bits, andtransmit the long truncated BSR informing of data volume for at leastone logical channel group among logical channel groups having data fortransmission, wherein the data volume for the at least one logicalchannel group is reported following an order that is determined based ona highest priority logical channel in each of the at least one logicalchannel group.
 2. The UE of claim 1, wherein the long truncated BSRcomprises: information indicating the logical channel groups having datafor transmission, and information regarding the data volume for the atleast one logical channel group.
 3. The UE of claim 1, wherein the orderis determined based on logical channel group identifiers, if prioritiesof highest priority logical channels are same.
 4. The UE of claim 1,wherein the highest priority logical channel in each of the at least onelogical channel group is selected regardless of whether correspondinglogical channel has data.
 5. The UE of claim 1, wherein the longtruncated BSR is transmitted as a padding BSR.
 6. The UE of claim 1,wherein the long truncated BSR is transmitted, if the number of paddingbits is equal to or larger than a size of a short BSR plus a subheaderof the short BSR, and is smaller than a size of a long BSR plus asubheader of the long BSR.
 7. The UE of claim 6, wherein the short BSRis a BSR that includes an identifier of a single logical channel andinformation regarding data volume for the single logical channel, andwherein the long BSR is a BSR that includes information regarding datavolume for each of the logical channel groups having data fortransmission.
 8. The UE of claim 7, wherein the long truncated BSR isclassified into a periodic BSR, a regular BSR, and a padding BSRdepending on a time during which the data is transmitted and an amountof information.
 9. A base station in a wireless communication system,the base station comprising: a transceiver; and at least one processorcoupled to the transceiver and configured to: receive, from a userequipment (UE), a long truncated buffer status report (BSR) informing ofdata volume for at least one logical channel group among logical channelgroups having data for transmission, the logical channel groups beingestablished at the UE, wherein the data volume for the at least onelogical channel group is reported following an order that is determinedbased on a highest priority logical channel in each of the at least onelogical channel group.
 10. The base station of claim 9, wherein the longtruncated BSR comprises: information indicating the logical channelgroups having data for transmission, and information regarding the datavolume for the at least one logical channel group.
 11. The base stationof claim 9, wherein the order is determined based on logical channelgroup identifiers, if priorities of highest priority logical channelsare same.
 12. The base station of claim 9, wherein the highest prioritylogical channel in each of the at least one logical channel group isselected regardless of whether corresponding logical channel has data.13. The base station of claim 9, wherein the long truncated BSR istransmitted as a padding BSR.
 14. The base station of claim 9, whereinthe long truncated BSR is transmitted, if the number of padding bits isequal to or larger than a size of a short BSR plus a subheader of theshort BSR, and is smaller than a size of a long BSR plus a subheader ofthe long BSR.
 15. The base station of claim 14, wherein the short BSR isa BSR that includes an identifier of a single logical channel andinformation regarding data volume for the single logical channel, andwherein the long BSR is a BSR that includes information regarding datavolume for each of the logical channel groups having data fortransmission.
 16. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver; and at least one processorcoupled to the transceiver and configured to: receive, from a basestation, first system information comprising atime-alignment-timer-common value, transmit, to the base station, arandom access preamble in order to transmit one of a first message forrequesting to resume a radio resource control (RRC) connection and asecond message for requesting second system information, receive, formthe base station, a random access response comprising a timing advanced(TA) command, after transmitting the random access preamble, start atime alignment timer that has a length indicated by thetime-alignment-timer-common value, and transmit one of the first messageand the second message.
 17. The UE of claim 16, wherein the at least oneprocessor is further configured to, if the time alignment timer expires,perform at least one of: flushing hybrid automatic repeat request (HARQ)buffers; releasing a physical uplink control channel (PUCCH); releasinga sounding reference signal (SRS); or clearing configured downlinkassignments and configured uplink grants.
 18. The UE of claim 16,wherein the at least one processor is further configured to transmit thefirst message to transition from an RRC inactive mode to an RRCconnected mode while the UE operates in the RRC inactive mode.
 19. TheUE of claim 16, wherein the at least one processor is further configuredto receive the second system information, after transmitting the secondmessage.
 20. The UE of claim 16, wherein the first system informationcomprises configuration information used to transmit the random accesspreamble.